The invention relates to a sensor device according to the preamble of Claim 1. A sensor device of this nature is known from EP 0,455,305, which shows a sensor which can rotate about a vertical axis and which generates horizontally directed laser beams which, by means of the rotation of the sensor, cover the horizontal plane. The position of the object to be detected is determined by recording the direction of the laser beam and the distance from the object to the sensor in the control unit. The drawback of the known device is that the position of the object is highly dependent on the direction of the laser beam, which therefore has to be determined with a high level of accuracy, and this is difficult to achieve. Also, the means of measuring the distance between the sensor and the object are relatively expensive. The object of the invention is to eliminate the abovementioned drawbacks, and to this end the sensor device is designed in accordance with the characterizing part of Claim 1. In this way, the sensor device is provided with simple radiation sources and detectors for determining the position of the object reliably and inexpensively.
According to a refinement, the sensor device is designed according to the characterizing part of Claim 2. This makes it easy to distinguish between the various radiation sources.
According to one embodiment, the sensor device is designed according to Claim 3. This provides a further distinction between the various radiation sources, with the result that if appropriate it is also possible for a plurality of sources to be activated simultaneously.
According to one embodiment, the sensor device is designed according to Claim 4. In this way, the position of the object can be established with greater accuracy.
According to one improved embodiment, the sensor device is designed according to Claim 5. In this way, it is simple to detect two or more objects in the operating area.
According to a further refinement, the sensor device is designed according to Claim 6. Positioning the radiation sources next to one another in a sensor unit makes them easy to position with accuracy.
According to a further refinement, the sensor device is designed according to Claim 7. This makes activation and switching of the radiation sources easier and avoids thick cables with many different cores leading from the control unit to the radiation sources.
The invention also comprises a milking device according to the preamble of Claim 8. A milking device of this nature is known from the document referred to above. Using the abovementioned sensor device in accordance with the characterizing part of Claim 6 results in an accurate and operationally reliable device.
According to one embodiment, the milking device is designed according to Claim 9. In this way, the teats can be located in a simple manner.
According to one embodiment, the milking device is designed according to the characterizing part of Claim 10. In this way, it is simple to detect the position of all the teats of the udder simultaneously.
The invention also comprises a sensor unit according to Claim 11. A sensor unit of this nature is compact and easy to install, and it is possible to generate a large detection field without the need for a large signal cable leading to the sensor unit.